In-progress generations were interrupted when a set_runtime_config
arrived mid-stream: the handler immediately stopped and restarted the
CLI subprocess. Track per-session busy state from outbound status
events and queue the restart, applying it (with the latest override,
collapsing multiple toggles) once the session returns to idle.
Bumps desktop app to 0.5.1 with matching release notes.
Tested: desktop tsc --noEmit; Windows x64 NSIS package + package-smoke.
Not-tested: check:server, desktop Vitest.
Scope-risk: narrow
Confidence: medium
